<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<style>

    div{
        width:200px;
        height:80px;
    }

    .a{
        background:blueviolet;
        position:relative;
        z-index:3;
    }

    .b{
        background-color:brown;
        position:relative;
        top:-20px;
        left:30px;
        z-index:2;
    }

</style>
<body>
    

    <div class="a"></div>
    <div class="b"></div>
</body>
</html>